1. Field of Invention
The invention relates to the technical field of a liquid crystal device having a structure comprising pixel electrodes arranged in a matrix, and particularly to the technical field of a liquid crystal device having a structure comprising a planarized interlayer insulating film provided below pixel electrodes.
2. Description of Related Art
As shown in FIG. 11, a conventional liquid crystal device 400 comprises a liquid crystal layer 50 held between a counter substrate 300 and a TFT array substrate 200. FIG. 10 is a plan view showing a TFT array substrate of a liquid crystal device, and FIG. 11 is a longitudinal sectional view of the liquid crystal device taken along line B-Bxe2x80x2 in FIG. 10, showing the vicinity of the region between adjacent pixel electrodes arranged along the data line direction.
As shown in FIGS. 10 and 11, the TFT array substrate 200 comprises a plurality of scanning lines 3 and a plurality of data lines 6, which are arranged to cross each other on a substrate 10 made of quartz, glass, or the like, a thin film transistor and a pixel electrode 9a electrically connected thereto at each of the intersections of the scanning lines 3 and the data lines 6, and capacitance lines 3b arranged in parallel with the scanning lines. Each of the thin film transistors comprises a semiconductor layer 1 shown by a dotted line, a gate insulating film 2, and a gate electrode 3a which comprises a portion of the scanning lines 3. Each of the pixel electrodes 9a is electrically connected to the semiconductor layer 1 through a contact hole 8, and a part of each of the data lines 6 functions as a source electrode 6a, and is electrically connected to the semiconductor layer 1 through a contact hole 5.
As shown in FIG. 11, in the TFT array substrate 200, a light shielding film 11a patterned in a predetermined shape, a base insulating film 12, the semiconductor film 1 formed in a predetermined shape, the gate insulating film 2, the scanning lines 3 and capacitance lines 3b, and an interlayer insulating film 4 are successively laminated on the substrate 10. Furthermore, the data lines 6 (not shown in FIG. 11), an interlayer insulating film 7 arranged to cover the data lines 6, and the pixel electrodes 9a are successively laminated on the interlayer insulating film 4.
On the other hand, the counter substrate 300 comprises a counter electrode 21 formed over the entire surface of the lower side.
In the liquid crystal device, the optical properties of liquid crystal molecules of the liquid crystal layer 50 located between the counter electrode 21 and the pixel electrodes 9a are changed by a potential difference between the voltage applied to the counter electrode 21 and the voltage applied to each of the pixel electrodes 9a. 
In the conventional liquid crystal device, in order to improve the display properties, the interlayer insulating film 7 provided below the pixel electrodes 9a is planarized to planarize the surface of the liquid crystal layer side of the TFT array substrate, preventing orientation defects from occurring in the liquid crystal molecules due to surface steps.
As shown in FIG. 11, for example, when voltages of different magnitudes are applied to the adjacent pixel electrodes 9a, transverse electric field C occurs in the vicinities of the regions between the adjacent pixel electrodes 9a. As a result, in the vicinities of the regions between the adjacent pixel electrode 9a, the direction of the liquid crystal molecules 50a are affected by the direction of the transverse electric field C. Therefore, the liquid crystal molecules in the vicinities of the regions between the adjacent pixel electrodes are not oriented in the desired direction, thereby causing orientation defects. In the defective liquid crystal orientation regions, the orientation direction of the liquid crystal molecules differs from that of regions where the liquid crystal molecules are normally oriented without being affected by the transverse electric field. As a result, bright lines referred to as xe2x80x9cdisclination linesxe2x80x9d occur, causing the problem of deteriorated display quality of the liquid crystal device. In addition, the pitch of the pixel electrodes has been recently decreased to increase the definition of the liquid crystal device, making the problem more serious.
Furthermore, a light shielding film 23 formed on the counter substrate side in order to conceal such display defects has the problem of significantly decreasing the aperture ratio of the pixel region.
The invention has been designed in consideration of the above-described problems, and one object of the invention is to provide a liquid crystal device causing no display defect and having a high aperture ratio.
One aspect of the invention relates to a liquid crystal device having a liquid crystal layer held between first and second substrates. A counter electrode is provided on the first substrate. Provided on the second substrate are pixel electrodes arranged in a matrix, switching elements respectively connected to the pixel electrodes, a lower interlayer insulating film having a planarized film and arranged on the switching elements, data lines provided on the lower interlayer insulating film, and a second interlayer insulating film arranged on the data lines below the pixel electrodes. A pattern film is arranged on the lower interlayer insulating film below the pixel electrodes so that the pattern film is located in the regions between the adjacent pixel electrodes arranged along the data lines or scanning lines.
In the above aspect of the invention, the pattern film is provided on the planarized surface of the substrate so that in the vicinities of the regions between adjacent pixel electrodes arranged along the scanning lines or the data lines, the magnitude of a longitudinal electric field produced between the end of each of the pixel electrodes and the counter electrode in the thickness direction of the liquid crystal layer is higher than that of an electric field (referred to as a xe2x80x9ctransverse electric fieldxe2x80x9d hereinafter) produced between the adjacent pixel electrodes in the transverse direction. Namely, by arranging the pattern film on the planarized substrate surface in the vicinities of the regions between the respective pixel electrodes, the distance between the pixel electrodes and the counter electrode in the vicinities of the regions between the respective pixel electrodes can be controlled easily. In addition, the thickness of the pattern film can be set to any desired value so that the distance between the pixel electrodes and the counter electrode can be set to a desired value to control the magnitude of the longitudinal electric field. This aspect of the invention has the effect of preventing orientation defects from occurring, due to the transverse electric field, and obtains a liquid crystal device having high display quality.
This aspect of the invention is particularly effective for a liquid crystal display which has significant display defects due to the transverse electric field, and which include a planarized second substrate. The pattern film having any desired thickness is arranged at a specified position of the second substrate having the planarized surface, to positively provide steps in the surface and prevent the occurrence of the transverse electric field between the pixel electrodes, thereby obtaining a liquid crystal device causing no display defect due to the transverse electric field.
The pattern film preferably is part of the same film that forms the data lines. This construction permits the simultaneous formation of the data lines and the pattern film, and thus the pattern film can be formed only by changing a pattern mask without increasing the number of the manufacturing steps.
A liquid crystal device according to this aspect of the invention includes a liquid crystal layer held between first and second substrates, a counter electrode provided on the first substrate, a plurality of scanning lines and a plurality of data lines arranged to cross each other, an upper interlayer insulating film arranged to cover the scanning lines and the data lines, a plurality of pixel electrodes respectively arranged at the intersections of the scanning lines and the data lines in a matrix on the upper interlayer insulating film, and a pattern film arranged on a planarized surface and below the upper interlayer insulating film so as to be located in the regions between the adjacent pixel electrodes arranged along the data lines or scanning lines, all of which are provided on the second substrate.
Preferably, the pattern film is provided on the planarized surface of the substrate so that in the vicinities of the regions between adjacent pixel electrodes arranged along the scanning lines or the data lines, the magnitude of a longitudinal electric field produced between the end of each of the pixel electrodes and the counter electrode in the thickness direction of the liquid crystal layer is higher than that of a transverse electric field produced between the adjacent pixel electrodes in the transverse direction. Namely, by arranging the pattern film on the planarized substrate surface in the vicinities of the regions between the respective pixel electrodes, the distance between the pixel electrodes and the counter electrode in the vicinities of the regions between the respective pixel electrodes can be controlled easily. In addition, the thickness of the pattern film can be set to any desired value so that the distance between the pixel electrodes and the counter electrode can be set to a desired value to control the magnitude of the longitudinal electric field. This aspect of the invention thus has the effect of preventing orientation defects from occurring due to the transverse electric field, to obtain a liquid crystal device having high display quality.
The invention is particularly effective for a liquid crystal display which has significant display defects due to the transverse electric field, and which includes a planarized second substrate. The pattern film having any desired thickness is arranged at a specified position of the second substrate having the planarized surface to positively provide steps in the surface and prevent the occurrence of the transverse electric field between the pixel electrodes, thereby obtaining a liquid crystal device causing no display defect due to the transverse electric field.
In addition, a light shielding film need not be provided on the first substrate side in order to conceal the defective display region caused by the transverse electric field, and thus the line width of a light shielding film on the counter substrate side can be narrowed, improving the aperture ratio of the pixel region.
Furthermore, the width of the regions between the adjacent pixel electrodes preferably is longer than the distance between the edges of the pixel electrodes and the counter electrode in the vicinities of the regions between the pixel electrodes. In this construction, in the regions between the adjacent pixel electrodes arranged along the scanning lines or data lines, the magnitude of an electric field produced between the edges of the pixel electrodes and the counter electrode can be increased securely, as compared with the magnitude of an electric field produced between the adjacent pixel electrodes, thereby causing the effect of preventing the occurrence of orientation defects due to the transverse electric field, and obtaining a liquid crystal device having high display quality.
Furthermore, preferably the edges of the pixel electrodes are overlapped with the pattern film. This construction has the effect of improving the aperture ratio of the display region.
Furthermore, the pattern film may be formed in the same layer as the data lines. This construction permits the formation of the pattern film at the same time as the data lines, and thus the pattern film can be formed only by changing a pattern mask without the need to increase the number of manufacturing steps. The pattern film may be formed in any pattern shape as long as the adjacent data lines are not electrically connected to each other. For example, the pattern film may be connected to the data lines.
Furthermore, the distance between the pattern film and each of the data lines may be not more than twice as long as the thickness of the upper interlayer insulating film. In this construction, when the pattern film is arranged between the data lines, there are spaces between the pattern film and the data lines to decrease steps in the spaces, thereby causing the effect of preventing the occurrence of orientation defects due to the transverse electric field between the data lines and the pattern film. Thus, there is the effect of improving the aperture ratio of the display region, and improving display quality.
The planarized lower interlayer insulating film is provided to cover the scanning lines. The data lines and the pattern film are provided on the lower interlayer insulating film so that the pattern film covers at least portions of the scanning lines. The upper interlayer insulating film is provided to cover the data lines and the pattern film.
In this construction, the lower interlayer insulating film is planarized to planarize the region of the surface of the second substrate which contacts the liquid crystal layer, and which contributes to display quality when the liquid crystal device is assembled. Therefore, the orientation defects due to surface steps of the second substrate are prevented from occurring in the display region, thereby exhibiting the effect of obtaining a liquid crystal device having high display quality. The pattern film is arranged at a specified position of the second substrate having the planarized surface to positively provide surface steps, preventing the occurrence of the transverse electric field between the pixel electrodes, and obtaining a liquid crystal device having no display defect due to a transverse electric field.
In this construction, even when the pattern film is partly formed on the scanning lines, the lower interlayer insulating film is formed between the scanning lines and the pattern film to prevent the occurrence of a short circuit. At the same time, the lower interlayer insulating film is partly formed between the pattern film and the data lines, thereby obtaining a liquid crystal device causing no short circuit between the data lines that are not electrically connected to the pattern film.
Furthermore, the lower interlayer insulating film preferably is an inorganic film. When the liquid crystal device having this construction is used as a light valve of a projector, for example, the lower interlayer insulating film is prevented from deteriorating due to light from a light source, thereby obtaining a high-quality projector.
In the liquid crystal device, generally, the liquid crystal layer side surface of the second substrate preferably has high flatness in order to improve display quality, and the lower interlayer insulating film with high flatness is required. As a material for obtaining such a film having high flatness, an organic film is superior to an inorganic film because the thickness can be increased easily. However, when the liquid crystal device having an organic lower interlayer insulating film is used as a light valve of a projector, particularly when used as a blue light valve, there is the problem of the organic film deteriorating due to blue light emitted from a light source. In order to avoid this problem, an inorganic film is used as the material for the lower interlayer insulating film. When using the inorganic film, for example, the surface of the inorganic film must be planarized by CMP treatment (mechanical polishing) in order to improve the flatness of the film. In the liquid crystal device using the planarized film as the lower interlayer insulating film, the pixel electrodes are arranged on the upper interlayer insulating film having high flatness, and thus the problem of display defects due to the transverse electric field produced between the adjacent pixel electrodes is significant. In order to prevent the occurrence of the display defects due to the transverse electric field, according to one aspect of the invention, the pattern film is provided to positively provide surface steps, controlling the distance between the pixel electrodes and the counter electrode, and preventing the occurrence of the transverse electric field.
Therefore, the invention can be applied to a liquid crystal device that uses a planarized inorganic insulating film like the liquid crystal device used as a blue light valve of a projector, to obtain a liquid crystal device having no display defect due to the transverse electric field.
A projector of the present invention includes a light source, a liquid crystal light valve for modulating incident light emitted from the light source according to image information, and a projection lens that projects the light modulated by the liquid crystal light valve. The liquid crystal light valve is the above-described liquid crystal device.
The projector having this construction has high quality. Particularly, by using an inorganic film as the lower interlayer insulating film in a blue light valve, the deterioration in the lower interlayer insulating film due to the light emitted from the light source can be prevented, obtaining a high-quality projector.
A method of manufacturing a liquid crystal device of the invention includes the steps of: (1) forming a counter electrode on a first substrate to form a counter substrate; (2) forming a plurality of scanning lines and a plurality of data lines on a second substrate so that the scanning lines and the data lines cross each other; (3) forming an upper interlayer insulating film to cover the plurality of scanning lines and data lines; (4) forming a plurality of pixel electrodes on the upper interlayer insulating film at the intersections of the scanning lines and the data lines; (5) forming a pattern film on a planarized surface below the upper interlayer insulating film so that the pattern film is located in the regions between the adjacent pixel electrodes arranged along the data lines or the scanning lines to form an array substrate; (6) arranging the counter substrate and the array substrate with a gap therebetween so that the counter electrode is opposed to the pixel electrodes; and (7) injecting a liquid crystal into the gap.
In the liquid crystal device manufactured by the above manufacturing method the pattern film is arranged on the planarized surface of a substrate so that in the vicinities of the regions between the adjacent pixel electrodes arranged along the scanning lines or the data lines, the magnitude of a longitudinal electric field produced between the edges of the pixel electrodes and the counter electrode in the thickness direction of the liquid crystal layer is higher than that of a transverse electric field produced between the adjacent pixel electrodes in the transverse direction. Namely, by arranging the desired pattern film on the planarized surface of the substrate in the vicinities of the regions between the pixel electrodes, the distance between the pixel electrodes and the counter electrode in the vicinities of the regions between the pixel electrodes can be controlled easily. Therefore, the thickness of the pattern film can be set to any desired value to set the distance between the pixel electrodes and the counter electrode to a desired value so that the magnitude of the longitudinal electric field can be controlled. As a result, the occurrence of orientation defects due to the transverse electric field can be prevented to cause the effect of obtaining a liquid crystal device having high display quality.
Particularly, the invention is effective for a liquid crystal device which uses the array substrate having a planarized surface, and which easily causes display defects due to the transverse electric field. The pattern film having a desired thickness is provided at a specified position of the second substrate having the planarized surface to positively provide steps in the surface, thereby preventing the occurrence of the transverse electric field between the pixel electrodes, and obtaining a liquid crystal device having no display defect due to the transverse electric field.
A method according to one aspect of the invention includes the steps of: (1) forming a lower interlayer insulating film having the planarized surface to cover the scanning lines; (2) simultaneously forming the data lines and the pattern film on the lower interlayer insulating film; and (3) forming the upper interlayer insulating film to cover the data lines and the pattern film. This construction permits the simultaneous formation of the data lines and the pattern film, and thus the pattern film can be formed only by changing a pattern mask without the need to increase the number of manufacturing steps. The pattern film may be formed in any shape as long as the adjacent data lines are not electrically connected to each other. For example, the pattern film may be connected to the data lines.
A liquid crystal device according to one aspect of the invention includes a liquid crystal layer held between first and second substrates. A counter electrode is provided on the first substrate. Pixel electrodes are arranged in a matrix, and switching elements are respectively connected to the pixel electrodes. A lower interlayer insulating film is arranged on the switching elements, data lines are provided on the lower interlayer insulating film, and an upper interlayer insulating film is provided on the data lines below the pixel electrodes. A pattern film is arranged between the lower and upper interlayer insulating films below the pixel electrodes to be located in the regions between the adjacent pixel electrodes arranged along the scanning lines. Drain electrodes are connected to the switching elements with a dielectric film provided therebetween, and a light shielding film, both of which are provided between the data lines and the scanning lines. The pattern film is arranged to overlap the scanning lines and the light shielding film.
In this construction, the pattern film is provided so that in the vicinities of the regions between the adjacent pixel electrodes arranged along the scanning lines, the magnitude of a longitudinal electric field produced between the edges of the pixel electrodes and the counter electrode in the thickness direction of the liquid crystal layer is higher than that of a transverse electric field produced between the adjacent pixel electrodes. This can prevent the occurrence of orientation defects due to the transverse electric field to obtain a liquid crystal device having high display quality. In addition, the pattern film is provided to overlap the light shielding film and the scanning lines, thereby securely shielding the vicinities of the scanning lines against light.
Preferably, the pattern film is formed in the same film as the data lines. Therefore, the pattern film can be formed at the same time as the data lines, and thus the pattern film can be formed only by changing the pattern mask without increasing the number of manufacturing steps.